code: def xloss(logits, labels, ignore=None):
      """
      Cross entropy loss
      """
      return F.cross_entropy(logits, Variable(labels), ignore_index=255)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  import torch
  import torch.nn.functional
  from torch import nn
  from torch.autograd import Variable
label_desc: Use image node_id 11 for calling a global function with example usage: xloss(logits, labels, ignore) and returns: F